Convection oven

ABSTRACT

A convection cooking oven includes a cooking cavity for receiving food product to be cooked, a door movable between an open condition and a closed condition relative to the cooking cavity and a heater for generating heat. A fan system is provided for moving heated air within the cooking cavity, the fan system operable in both a first mode in which air is moved at a first rate, and a second mode in which either (i) air is moved at a second rate, which is lower than the first rate, or (ii) air is not moved by the fan system. A fan system override control is configured such that, when the fan system is operating in the first mode, the fan system is automatically switched to operate in the second mode based upon occurrence of a first predefined oven condition.

TECHNICAL FIELD

This application relates generally to commercial cooking ovens and, more specifically, to convection ovens.

BACKGROUND

In commercial kitchens (e.g., found in restaurant, cafeteria and retail environments), convection ovens are used for cooking a large variety of food items. Such ovens may utilize heaters in the form of either gas-burners or electric elements (e.g., resistive heaters) for generating heat, in combination with one or more fans to move heated air within the oven. Commercial kitchens are high volume cooking environments in which the door of the oven is repeatedly being opened and closed, which can result in large energy losses. Leakage past the oven door seals and through a steam vent in the oven also occur, even when the oven door is closed and the oven is simply idling (e.g., in a ready state waiting for an operator to place an item to be cooked into the oven).

Typical convection ovens may have a high fan speed and a low fan speed, where the fan speed is manually controlled by an operator using a switch or other input on the oven interface. The higher the fan speed, the higher the volumetric flow rate of air and, thus, the higher the energy losses (e.g., due to higher leakage around door seals etc.). Operators commonly run the fan at high speed because the high speed tends to produce a more even bake. As a result, for efficiency rating purposes, the ovens are also tested with the fan at high speed, which adversely impacts efficiency.

Accordingly, it would be desirable to provide a convection oven configured to control fan speed in a more effective manner that increases oven efficiency.

SUMMARY

In one aspect, a cooking oven includes a fan speed control that reduces energy losses by automatically switching a fan system to produce a lesser flow rate under one or more predefined oven conditions.

In another aspect, a convection cooking oven includes a cooking cavity for receiving food product to be cooked and a door movable between an open condition and a closed condition relative to the cooking cavity. The oven includes a heater for heating air, and a fan system for moving heated air within the cooking cavity, where the fan system is operable in a first mode for moving air at a first rate or in a second mode for moving air at a second rate, wherein the first rate is higher than the second rate. A user interface includes a control input for manually selecting one of the first mode or the second mode for operation of the fan system. A fan system override control is configured such that, when the first mode is manually selected, the fan system is automatically switched to operate in the second mode based upon occurrence of a first predefined oven condition.

In still another aspect, a convection cooking oven includes a cooking cavity for receiving food product to be cooked, a door movable between an open condition and a closed condition relative to the cooking cavity and a heater for generating heat. A fan system is provided for moving heated air within the cooking cavity, the fan system operable in both a first mode in which air is moved at a first rate, and a second mode in which either (i) air is moved at a second rate, which is lower than the first rate, or (ii) air is not moved by the fan system. A fan system override control is configured such that, when the fan system is operating in the first mode, the fan system is automatically switched to operate in the second mode based upon occurrence of a first predefined oven condition.

In yet another aspect, a convection cooking oven includes a cooking cavity for receiving food product to be cooked, and a heating system including a heater and a fan for moving heated air within the cooking cavity, the fan operable in a first mode for moving air at a first rate or in a second mode for moving air at a second rate, wherein the first rate is higher than the second rate. A user interface includes a control input for selecting one of the first mode or the second mode for operation of the fan system. A fan override is control configured such that, when the first mode is selected, the fan automatically switches to operate in the second mode based upon occurrence of a predefined oven condition.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a convection oven;

FIG. 2 is a schematic view of the oven interface;

FIG. 3 is a schematic view of the oven; and

FIG. 4 is an exemplary flow chart of oven operation.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, a convection cooking oven 10 includes an external housing 12 and an internal housing 13 defining a cooking cavity 14 for receiving food product to be cooked. One or more doors 16 are movable between an open condition and a closed condition relative to the cooking cavity. One or more heaters 18 is provided for generating heat. Here, resistive heating elements are shown, but other heater types (e.g., gas) could be utilized.

A fan system 20 is provided for moving heated air within the cooking cavity 14 to more effectively and evenly heat loaded food product. Here, the fan system 20 is formed by a single fan 22 and fan motor 24 located along a back wall 26 of the cavity 14, in alignment with an opening 28 of the back wall. However, in other embodiments, multiple fans could be used. The fan system is operable in a first mode (e.g., high fan speed) for moving air at a high rate or in a second mode (e.g., low fan speed) for moving air at a low rate. In the illustrated embodiment, operation of the fan 22 pulls air from the oven cavity, moves the air past the heaters and alongside the exterior of the cavity walls, and then back into the cavity in a circulating manner. However, other variations of convection air flow are possible and within the scope of this application.

A user interface 30 includes a control input 32 (here a switch) for manually selecting one of the first mode or the second mode for fan system operation. The illustrated interface 30 also includes a temperature control knob 34, a timer control knob 36, master switch 38 and a light control switch 40. In other embodiments, the user interface could be more advance, such as employing a touch-screen interface.

A controller 50 is responsive to the user interface inputs. The controller 50 may take on various forms, incorporating electrical and electronic circuitry and/or other components. As used herein, the term controller is intended to broadly encompass any circuit (e.g., solid state, application specific integrated circuit (ASIC), an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA)), processor(s) (e.g., shared, dedicated, or group—including hardware or software that executes code), software, firmware and/or other components, or a combination of some or all of the above, that carries out the control functions of the machine or the control functions of any component thereof.

Regardless of the exact configuration of the controller 50, the controller is configured with a fan system override control 52 that, in turn, is configured such that, when the first mode for the fan system is manually selected by use of the switch 32, the fan system will automatically be switched to operate in the second mode based upon occurrence of a predefined oven condition. More specifically, the predefined oven condition is selected such that the fan system operates in the first mode primarily when the higher convection air flow rate is most needed, and switches to the second mode when a lower convection flow rate will not adversely impact the cooking operation.

By way of example, the predefined operating condition may be a call for heat condition of the oven (e.g., based upon whether the heater(s) are turned ON or OFF). In this example, when the first mode is selective or otherwise active, the first mode will be maintained while the oven is heating up (heaters on) and the second mode will be automatically triggered when the oven reaches the designated temperature set point for the cooking operation (at which point the heaters turn off). The fan system override control 52 may include a relay, the state of which is controlled by current flow, or lack thereof, through the heaters 16, to achieve the override result. Thus, the fan system override control also automatically switches the fan system back to the first mode when appropriate (e.g., when current flow the heater(s) resumes)).

Thus, the override operation allows the oven to operate with reduced energy losses when the higher convection flow rate is not actually needed for the cooking operation. The override reduces current draw during part of the cooking cycle and during a majority of the time the oven is in an idle state (running with no food in the cavity). The override also reduces the amount of air leakage due to the lower convection flow rate. Further, the switching between the convection flow rates beaks up standing waves of air flow in the oven, which improves overall baking consistency.

Various predefined oven conditions could be implemented for the purpose of the fan system override control. The predefined oven condition may be a temperature condition of the cooking cavity (e.g., indicated by temperature sensor/thermostat 42). For example, the temperature condition may be a temperature of the cooking cavity reaching either a temperature set point for cooking or a predefined temperature that is below the temperature set point for cooking. The flow chart 100 FIG. 4 depicts oven operation when the fan speed setting is either set to HI or LO. By way of example, the ON condition 102 may be controlled by master switch, and the fan speed setting condition 104 may be controlled by the switch 32. As depicted in the right side of the flow chart, when the fan is set to the HI mode, the fan runs at HI per 106, but can automatically switch to the LO mode, per 112, when the sensed temperature reaches the temperature set point, per 108, and the heater turns off per 110. In this case, the override of the fan speed setting triggers off of the call for heat according to whether the actual oven temperature is at the set point. More generally, however, as used herein, a “call for heat condition” of the oven encompasses oven conditions in which the oven controller is configured to activate the heater(s), regardless of how the call for heat condition is determined to exist (e.g., direct sensing of temperature or sensing of current flow to the heater(s)). Once the temperature falls back below the set point, the heater is turned back on, per 114, and the fan is switched back to the HI mode, per 116. Notably, in this example, when the fan is set to the LO mode by the switch per 104, the LO mode is maintained and there is no override that switches the fan back to the HI mode, per 118, 120, 122 and 124.

As another example, the temperature condition may be a temperature of the cooking cavity remaining within a predefined range of a temperature set point for at least a set time period (e.g., actual temperature no less than ten degrees below the set point for five minutes or ten minutes). As another example, the temperature condition may be a temperature change condition (e.g., falling temperature triggers second mode, rising temperature returns to first mode). As another example, the temperature condition may be a rate of temperature change condition (e.g., as long as the rate of change is below a set threshold, the second mode is triggered). Other variations are also possible.

The first mode may result in a first effective (average) fan motor operating speed and the second mode may result in a second effective fan motor operating speed, where the first effective fan motor operating speed is faster than the second effective fan motor operating speed. Although a simple change in actual fan speed is primarily contemplated above as corresponding to the effective fan speeds, other variations are possible. For example, the effective speeds may be achieved by pulsed operation of the fan motor according to respective duty cycles for the first mode and the second mode.

In another variation, the fan system may include multiple fans, and in the first mode two or more fans run, and in the second mode at least one of the two or more fans does not run.

It is to be clearly understood that the above description is intended by way of illustration and example only, is not intended to be taken by way of limitation, and that other changes and modifications are possible. For example, ovens which do not include a manual fan speed control input could also employ a fan system override control as contemplated above, with the fan system operating in the first mode at all times when the predefined oven condition is not detected or present. As another example, in the second mode, the convection air flow may be stopped entirely. Other variations are possible. 

What is claimed is:
 1. A convection cooking oven, comprising: a cooking cavity for receiving food product to be cooked; a door movable between an open condition and a closed condition relative to the cooking cavity; a heater for heating air; a fan system for moving heated air within the cooking cavity, the fan system operable in a first mode for moving air at a first rate or in a second mode for moving air at a second rate, wherein the first rate is higher than the second rate; a user interface including a control input for manually selecting one of the first mode or the second mode for operation of the fan system; and a fan system override control configured such that, when the first mode is manually selected, the fan system is automatically switched to operate in the second mode based upon occurrence of a first predefined oven condition.
 2. The convection cooking oven of claim 1, wherein the first predefined oven condition comprises a call for heat condition of the oven.
 3. The convection cooking oven of claim 1, wherein the first predefined oven condition comprises a temperature condition of the cooking cavity.
 4. The convection cooking oven of claim 3, wherein the temperature condition is a temperature of the cooking cavity reaching either a temperature set point for cooking or a predefined temperature that is below the temperature set point for cooking.
 5. The convection cooking oven of claim 3, wherein the temperature condition is a temperature of the cooking cavity remaining within a predefined range of a temperature set point for at least a set time period.
 6. The convection cooking oven of claim 3, wherein the temperature condition is a temperature change condition.
 7. The convection cooking oven of claim 3, wherein the temperature condition is a rate of temperature change condition.
 8. The convection cooking oven of claim 1, wherein the first mode establishes a first effective fan motor operating speed and the second mode establishes a second effective fan motor operating speed, the first effective fan motor operating speed being faster than the second effective fan motor operating speed.
 9. The convection cooking oven of claim 8, wherein at least the second effective fan motor operating speed is achieved by pulsed operation of a fan motor associated with a fan of the fan system.
 10. The convection cooking oven of claim 1, wherein the fan system comprises both a first fan and a second fan, in the first mode both the first fan and the second fan run, and in the second mode the first fan runs and the second fan does not run.
 11. The convection cooking oven of claim 1, wherein the fan system override control is further configured such that, when the fan system is operating in the second mode as a result of the fan override control, the fan system override control will automatically switch the fan system back to the first mode based upon occurrence of a second predefined oven condition.
 12. The convection cooking oven of claim 11, wherein the second predefined oven condition comprises the absence of the first predefined oven condition.
 13. A convection cooking oven, comprising: a cooking cavity for receiving food product to be cooked; a door movable between an open condition and a closed condition relative to the cooking cavity; a heater for generating heat; a fan system for moving heated air within the cooking cavity, the fan system operable in both a first mode in which air is moved at a first rate, and a second mode in which either (i) air is moved at a second rate, which is lower than the first rate, or (ii) air is not moved by the fan system; a fan system override control configured such that, when the fan system is operating in the first mode, the fan system is automatically switched to operate in the second mode based upon occurrence of a first predefined oven condition.
 14. The convection cooking oven of claim 13, wherein the first predefined oven condition comprises a call for heat condition of the oven.
 15. The convection cooking oven of claim 13, wherein the first predefined oven condition comprises a temperature condition of the cooking cavity.
 16. The convection cooking oven of claim 15, wherein the temperature condition is one of: (a) a temperature of the cooking cavity reaching either a temperature set point for cooking or a predefined temperature that is below the temperature set point for cooking; or (b) a temperature of the cooking cavity remaining within a predefined range of a temperature set point for at least a set time period; or (c) a temperature change condition; or (d) a rate of temperature change condition.
 17. The convection cooking oven of claim 13, wherein the fan system override control is further configured such that, when the fan system is operating in the second mode, the fan override control will automatically switch the fan system back to the first mode based upon occurrence of a second predefined oven condition.
 18. The convection cooking oven of claim 17, wherein the second predefined oven condition comprises the absence of the first predefined oven condition.
 19. A convection cooking oven, comprising: a cooking cavity for receiving food product to be cooked; a heating system including a heater and a fan for moving heated air within the cooking cavity, the fan operable in a first mode for moving air at a first rate or in a second mode for moving air at a second rate, wherein the first rate is higher than the second rate; a user interface including a control input for selecting one of the first mode or the second mode for operation of the fan system; and a fan override control configured such that, when the first mode is selected, the fan automatically switches to operate in the second mode based upon occurrence of a predefined oven condition.
 20. The convection cooking oven of claim 19, wherein the predefined oven condition comprises a call for heat condition of the oven. 